At present, an exchange network implements data exchange between exchange access apparatuses in an exchange system. The exchange network is divided into a single-stage exchange network and a three-stage CLOS exchange network. The single-stage exchange network is simple in networking and small in capacity. The three-stage CLOS exchange network is complicated in networking and large in capacity. The single-stage exchange network is simple in networking with each link corresponding to only one access apparatus, so the situation where a plurality of access apparatuses share a link does not exist. Therefore, data streams to different access apparatuses in the exchange network will not affect each other.
In the three-stage CLOS exchange network, as shown in FIG. 1, it is composed of three stages of exchange units. Cells sent by the access apparatus reaches to a destination access apparatus via a three-stage exchange apparatus respectively. In first-stage exchange and second-stage exchange, a link may reach to a plurality of access apparatuses. Therefore, data streams arriving to different access apparatuses will affect each other. A traditional load balancing method performs load balancing in all links instead of distinguishing data streams. Therefore, it may be caused that a data stream arriving to a certain apparatus is transmitted in one or more links, thereby causing the problems of local congestion and bandwidth waste of the data stream.
Data is transmitted in the exchange network on the basis of a cell unit. As shown in FIG. 2, a first-stage exchange apparatus receives cells sent to an access apparatus N−1 and an apparatus N, and two links may both reach to the destination access apparatus currently. In accordance with a traditional load balancing mode, these two links do not distinguish destinations of the cells. Therefore, the cells sent in these two links in a polling way, for example, the first cell is sent to a second-stage exchange apparatus 0, the second cell is sent to a second-stage exchange apparatus 1, the third cell is also sent to the second-stage exchange apparatus 0, and so on. So, all the cells sent to the access apparatus N−1 are sent to the second-stage exchange apparatus 0, and then sent to a third-stage exchange apparatus N−1; and all the cells sent to the access apparatus N are sent to the second-stage exchange apparatus 1, and then sent to a third-stage exchange apparatus N. A final result is that: all the cells sent to the access apparatus N−1 are congested in the third-stage exchange apparatus N−1, and all the cells sent to the access apparatus N are congested in the third-stage exchange apparatus N. Meanwhile, only one of these two links of the destination access apparatuses N and N−1 receives the cells, and the bandwidths of the other link are completely wasted.
As above, the traditional load balancing method cannot ensure that cells arriving to each destination access apparatus are balanced across all accessible links. The load balancing method may cause congestion of cells in a certain exchange apparatus, so the exchange capability is reduced, and meanwhile, bandwidth waste will be caused.